Recently, due to the development of mobile Internet through mobile terminals such as smartphones, a plurality of services including an mVoIP call service have been developed.
This mVoIP is technology that can use an Internet phone using a terminal through Wi-Fi (a wireless LAN) and wireless mobile Internet such as a 3G network. A transmission rate of the mVoIP is lower than that of a VoIP. However, as Internet-enabled terminals such as a smartphone become popular, the number of mVoIP subscribers has rapidly increased. It is no exaggeration to say that all users of Internet-enabled terminals are potential mVoIP users.
However, up to now, in call originating for an mVoIP call, preprocessing of network address translation (NAT) information acquisition and signaling such as a session initiation protocol (SIP) is necessary in the terminal. Therefore, much preprocessing time is necessarily required until an actual call is connected.
Accordingly, due to a preprocessing time after the mVoIP call is made, that is, a call waiting time, a service quality degrades and users complain about the service. Therefore, there is an urgent need to develop technology for reducing a waiting time taken for the mVoIP call.